Aesop's Fables, translated by Laura Gibbs (2002)

A shepherd found some wolf cubs and he brought them up, thinking that
the fully grown wolves would both guard his flock and steal other people's
sheep to bring back to his sheepfold. But when the cubs grew up, the first
thing they did was to destroy the man's own flock. The man groaned and
said, 'It serves me right! Why didn't I kill them when they were little?'
The story shows that when people harbor a criminal they become his
first victims without even realizing it.